TY  - JOUR
AU  - Borghans, Bart
AU  - Kortzak, Daniel
AU  - Longo, Piersilvio
AU  - Kolen, Bettina
AU  - Machtens, Jan-Philipp
AU  - Fahlke, Christoph
TI  - Allosteric modulation of proton binding confers Cl- activation and glutamate selectivity to vesicular glutamate transporters
JO  - PLoS Computational Biology
VL  - 21
IS  - 6
SN  - 1553-734X
CY  - San Francisco, Calif.
PB  - Public Library of Science
M1  - FZJ-2025-03030
SP  - e1013214 -
PY  - 2025
AB  - Vesicular glutamate transporters (VGLUTs) fill synaptic vesicles with glutamate andremove luminal Cl- via an additional anion channel mode. Both of these transportfunctions are stimulated by luminal acidification, luminal-positive membrane potential,and luminal Cl-. We studied VGLUT1 transporter/channel activation using acombination of heterologous expression, cellular electrophysiology, fast solutionexchange, and mathematical modeling. Cl- channel gating can be described with akinetic scheme that includes two protonation sites and distinct opening, closing, andCl--binding rates for each protonation state. Cl- binding promotes channel openingby modifying the pKa values of the protonation sites and rates of pore opening andclosure. VGLUT1 transports glutamate and aspartate at distinct stoichiometries:H+-glutamate exchange at 1:1 stoichiometry and aspartate uniport. Neurotransmittertransport with variable stoichiometry can be described with an alternating accessmodel that assumes that transporters without substrate translocate in the doubly protonatedstate to the inward-facing conformation and return with the bound amino acidsubstrate as either singly or doubly protonated. Glutamate, but not aspartate, promotesthe release of one proton from inward-facing VGLUT1, resulting in preferentialH+-coupled glutamate exchange. Cl- stimulates glutamate transport by making theglutamate-binding site accessible to cytoplasmic glutamate and by facilitating transitionsto the inward-facing conformation after outward substrate release. We concludethat allosteric modification of transporter protonation by Cl- is crucial for both VGLUT1transport functions.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.1371/journal.pcbi.1013214
UR  - https://juser.fz-juelich.de/record/1044114
ER  -